The invention relates to improvements in so-called trimming or equalizing apparatus which can be utilized with advantage in the tobacco processing industry to remove the surplus from a moving stream of fibrous material, such as particles of tobacco or particles of filter material for tobacco smoke. Trimming or equalizing apparatus of the class to which the present invention pertains can be utilized in so-called rod making machines for the mass production of plain cigarettes, cigars or cigarillos. The following description will discuss primarily trimming or equalizing apparatus which are used for the removal of surplus from moving tobacco streams; however, it is to be understood that the apparatus can be utilized with equal or similar advantage for the removal of surplus from streams or similar accumulations containing other types of materials including filter material for tobacco smoke.
As a rule, surplus tobacco is removed from a moving continuous stream by an apparatus which defines a channel for the stream and employs a foraminous belt conveyor cooperating with a suction chamber to advance the stream in the channel past two coplanar trimming discs which extend into the stream so that the surplus is located at one side and the remaining (trimmed or equalized) stream is located at the other side of the common plane of the discs. The marginal portions of the discs clamp the stream in such a way that the surplus extends beyond their common plane and is removed by a rotary implement in the form of a paddle wheel or a cylindrical brush whose axis of rotation is inclined with reference to the direction of advancement of the stream in the channel. The paddles or the bristles sweep the surplus away from the remainder of the stream, not only at the locus where the marginal portions of the discs come nearest to each other but also upstream and downstream of such locus. The particles which are located upstream and downstream of the aforementioned locus are not clamped by the discs so that they, and some particles which are interlaced therewith, are actually extracted from the mass of tobacco particles at the other side of the common plane of the discs. This affects the appearance and density of the trimmed stream because the bristles or paddles remove the surplus as well as varying quantities of material which is supposed to form part of the trimmed stream, i.e., which should not be removed from the stream. The quality of the trimming or equalizing action is not improved by causing the marginal portions of the discs to move at a speed having, at the aforementioned locus, a component of movement in the direction of advancement of the stream which matches or approximates the speed of the stream.
Commonly owned U.S. Pat. No. 4,651,755 granted Mar. 24, 1987 to Rudszinat discloses an apparatus for trimming a stream of smokable material. The apparatus of Rudszinat employs a substantially disc-shaped surplus removing member having a slightly conical peripheral surface and a slightly conical front surface. The neighboring portions of the two surfaces are notched so that the peripheral surface is provided with teeth which are to segregate the surplus from the remaining major portion of the moving stream. The relatively wide peripheral surface of the disc can remove tobacco particles at the upstream side and/or at the downstream side of the location where the marginal portions of the two discs come nearest to each other.
The disclosure of the patent to Rudszinat is incorporated herein by reference.